Carbon nanotubes (CNT) have been the subject of intense research since their discovery in 1991. CNT's possess unique properties such as small size and electrical conductivity, which makes them suitable in a wide range of applications, including use as structural materials in molecular electronics, nanoelectronic components, and field emission displays. Carbon nanotubes may be either multi-walled (MWNTs) or single-walled (SWNTs), and have diameters in the nanometer range.
Depending on their atomic structure CNT's may have either metallic or semiconductor properties, and these properties, in combination with their small dimensions makes them particularly attractive for use in fabrication of nano-devices. A major obstacle to such efforts has been the diversity of tube diameters, chiral angles, and aggregation states in nanotube samples obtained from the various preparation methods. Aggregation is particularly problematic because the highly polarizable, smooth-sided fullerene tubes readily form parallel bundles or ropes with a large van der Waals binding energy. This bundling perturbs the electronic structure of the tubes, and it confounds all attempts to separate the tubes by size or type or to use them as individual macromolecular species. One method to disperse these aggregates is by the use of stabilized solutions of nucleic acid molecules as described in U.S. Ser. No. 60/432,804 and U.S. Ser. No. 60/428,087 incorporated herein by reference.
Co-incident with the problem of dispersion of aggregated carbon nanotubes is the problem of separation. Because most populations of nanotubes are aggregated it has been very difficult to obtain discreet populations of nanotubes that have a uniform length, diameter, chirality or other physical properties. The ability to perform such separations will be essential if carbon nanotubes are to be effectively used in electronics and other applications at the nano-scale.
Jiang et al (Journal of Colloid and Interface Science (2003), 260(1), 89-94 have demonstrated that populations of nanotubes may be dispersed in surfactant and separated by precipitation however no attempt was made to characterize the fractions on the basis of common physical or chemical parameters.
The problem to be solved, therefore, is to provide a method for the facile and inexpensive separation of dispersed carbon nanotubes into populations having discreet characteristics. Applicants have solved these problems through the use of stabilized solutions of nucleic acid molecules that have the ability to disperse and solubilize carbon nanotubes, resulting in the formation of nanotube-nucleic acid complexes. Applicants have discovered a method for the separation of these nucleic acid associated carbon nanotubes based on common chromatographic means. Although complexes of nucleic acids and carbon nanotubes are known, the present complexes are new, in that the association between the nanotube and nucleic acid is non-covalent and not through the interaction of specific functionalized groups.